Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

The Sooam Biotech Research Foundation said in a statement that the cloned Tibetan mastiff dogs were born in April, two months after being requested by the Chinese Academy of Sciences.

The foundation said it takes two months to produce cloned dogs from pregnancy, but it declined to discuss its success rate, citing internal policy.

The foundation also that all 17 dogs had been cloned from two Tibetan mastiffs — female and male — through six surrogate dogs, citing blind DNA tests by another institute.

However, an official of Kogene Biotech, the Seoul-based institute specializing in DNA analysis that did the tests, said it did not to take its own samples from the dogs and that the samples it tested were provided by the foundation.

Kogene Biotech said it did not know for certain if the samples came from cloned animals or the original dogs, or a combination of both, the official said. He spoke on condition of anonymity because he was not authorized to speak to the media.

In 2005, Hwang and his team of Seoul National University scientists successfully created the world’s first known dog clone, an Afghan hound named Snuppy, an achievement that was independently confirmed.

Hwang scandalized the international scientific community in 2005 when his breakthrough human cloning research involving embryonic stem cells was found to have been faked.